I kind of envisioned that one might install the sheer clamp in the hull, then use the outside of the clamp as a gluing surface and to provide some stiffness as you then compressed it all with tape

I think we are all talking about the same thing here, the problem that can arise with vertical sides at the sheer is ensuring that the deck is tight against the sheerclamp.

I sketched the two situations below, as you can maybe see in the first sketch (vertical sides) there has to something to pull the deck against the sheerclamp, unlike the second, where the angle between the deck and hull pretty well ensures a tight fit.